Background of the Invention
The invention and its various embodiments relate to methods and equipment for treating a vapor dominated discharge of process waste streams containing odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds having commingled gas, liquid, and/or solid phases generated at a wide variety of industrial, commercial, and environmental processes, including, but not limited to, pet food manufacturing, food processing, food cooking, energy generation, indoor air pollution control, environmental remediation and mitigations, refining, petrochemical, chemical manufacturing, machining, printing, electronics, wood products, textiles, pulp and paper. More specifically, the invention and its various embodiments relate to the removal of odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds contained in a multi-phase vapor waste exhaust stream having chemical vapors, solid particulates, smoke particulates, aerosols, and/or water vapor using several synergistic serial combinations of gas treatment processes specifically tasked to remove each type and phase of matter including, but not be limited to, staged condensation from near ambient to cryogenic temperatures, all manner and type of particulate removal, advanced oxidation, and/or the numerous wet scrubbing techniques.
Description of Related Art
Control of odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds contained in multi-phase vapor waste streams of commingled gas, liquid, and/or solid phases is one of the most challenging problems faced by all facets of industrial and energy production, including the animal byproduct processing industry, referred to as “rendering.” Processes designed for such control use thermal incineration (e.g. the firebox of industrial steam boilers, direct fired thermal oxidizer (“TO”), regenerative thermal oxidizer (“RTO”), regenerative catalytic oxidizer (“RCO”), thermal recuperative oxidizer (“TRO”), etc.) which are considered the current Best Available Control Technology (“BACT”). In most rendering facilities, animal byproduct is brought into a rendering plant and processed into numerous waste streams and products. Specifically, this process converts the byproduct, which consists of fresh and rotted waste animal tissue and bone, into a stable value- added material such as purified animal fats (lard, tallow, and grease) and protein meals (meat, bone meal, and blood meal). However, operation of this type of facility results in the production of various process-step specific vapor dominated process waste discharges having commingled gas, liquid, and/or solid phases containing odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds gases that must be discharged, ultimately, to breathing spaces and/or the atmosphere.
The rendering process involves multiple steps. The following is an example of some, but not all, processes that create vapor dominated commingled gas, liquid, and/or solid process waste streams at rendering plants. First, the raw material is brought to the plant in trucks and staged for input into the raw material conveyor to the raw material grinder and the raw material metering bin. The resulting commingled gas, liquid, and/or solid waste is typically contained by a room air ventilation system and vented to breathing spaces and/or the atmosphere or treated by a number of methods (e.g. spray scrubbing, packed bed wet scrubbing, etc.). The raw animal byproduct is then “cooked” in a continuous or batch cooker (e.g., disk dryer or other processes) to evaporate moisture and to separate fat from bone and protein. The resulting material is then separated into liquid fat and solids. The resulting vapor dominated discharge of process waste streams comprising odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds, and having commingled gas, liquid, and/or solid phases from the cooker process, contains significant quantities of fats and solid materials that are not completely separated. In addition, smoke can be generated during the cooking process. Cooking produces smoke, solid particulates, volatile organic compounds (“VOCs”), other volatile compounds such as hydrogen sulfide and ammonia, semi-volatile organic compounds (“SVOCs”), aerosolized fats, oils, greases, tallow, and wax and abundant water vapor. After cooking, the solids are processed to remove additional moisture and fats (e.g., by using a screw press) resulting in the generation of a press cake that is ultimately made into a meal product. The screw press process adds frictional heating and mechanical mixing while containing heat from the cooking process which, all together, produces a vapor dominated multi-phase process waste stream having a commingled gas, liquid, and/or solid phases comprising odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds substances. The screw press waste stream contains smoke, solid particulates, VOCs, other volatile compounds such as hydrogen sulfide and ammonia, SVOCs, aerosolized fats, oils, greases, tallow, and wax and water vapor. Solids generated in the screw press are further subject to additional frictional heating within the auger conveyance to the grinding room and in the multi-stage grinding processes. Frictional heating in these processes evolves waste smoke, solid particulates, VOCs, other volatiles such as hydrogen sulfide and ammonia, SVOCs, aerosolized fats, oils, greases, tallow, and wax and water vapor. The liquid fat and/or fat-liquid-solid slurries are processed to remove additional gases, liquids, and/or solids (e.g., by using an evaporator system followed by a centrifuge of the fats) resulting in a liquid fat product that can be further processed into fat-based products. The evaporator and centrifuge processes results in heating under vacuum to boil off vapors, mechanical mixing, aeration while containing heat from the cooking process results in the creation of a waste commingled vapor dominated vapor dominated multi-phase process waste stream containing VOCs, other volatiles such as hydrogen sulfide and ammonia, SVOCs, aerosolized fats, oils, greases, tallow, and wax and water vapor.
Vapor dominated discharge of process waste streams having commingled gas, liquid, and/or solid phases are generated at several points in the rendering process, including, but not limited to, the unloading, conveyance, grinding of raw material followed by cooking, screw press, auger conveyance, grinding room, evaporator and centrifuge. These vapor dominated multi-phase waste streams typically contain, but are not be limited to solid organic and inorganic particulates, smoke particulates, aerosolized oils greases, tallows, waxes and water vapor having odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds such as hydrogen sulfide, ammonia, carboxylic acids, esters, alcohols, ketones, aldehydes, amines, mercaptans, alkenes, furans, pyrazines, pyrroles, thiazoles, pyridine and other VOCs and SVOCs.
In most facilities a gaseous odor control system is used to reduce or remove some of these odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds vapor dominated process waste discharges having commingled gas, liquid, and/or solid phases from the numerous rendering processes. For example, the vapor dominated discharge of process waste streams having commingled gas, liquid, and/or solid phases from the cooker may be sent through an ambient temperature air or water cooled condenser to partially condense those commingled gas, liquid, and/or solid phases capable of being condensed and passing the condensed material to a waste water treatment system. The remaining vapor dominated waste discharge containing partially condensed odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds commingled gas, liquid, and/or solid phases is then sent to a gaseous odor control system such as an air scrubbing process or wet scrubber (e.g. spray condensers, spray venturi scrubbers, packed bed wet scrubbers, etc.) in which at least some of the multi-phase odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds materials are captured by chemical and physical mechanisms into a scrubbing solution and the resulting scrubbed vapor dominated commingled gas, liquid, and/or solid phases are released into breathing spaces and/or the atmosphere. However, such scrubbing processes do not remove enough of the odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds in the vapor dominated commingled gas, liquid, and/or solid phases. In many instances, these “high intensity vapors” are incinerated in numerous processes, including, but not limited to steam boilers, TOs, RTOs, RCOs, TROs that are considered BACT. The various methods of incineration do not address particulate matter treatment (e.g. PM2.5 and PM10), lose efficiency due to corrosive and erosive vapor dominated multi-phase process waste streams, increase maintenance and reduce equipment service life, produce odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds air pollution and ozone precursors (e.g. nitrogen oxides (NOx), sulfur oxide (SOx)), which can have a large carbon footprint due to burning of natural gas and petroleum fuels and be very expensive to construct, operate, and maintain. NOx is a lung irritant and is a major precursor to the formation of ozone smog. SOx is a lung irritant and long-term exposures to low concentration, mass, and volumes cause lung function damage. SOx is also a precursor to acid rain. Since ammonia and hydrogen sulfide are the most highly concentrated compounds in rendering plant vapor dominated commingled gas, liquid, and/or solid phase process discharges, incineration will result in significantly higher production of NOx and SOx as compared with VOC thermal oxidation alone. Combined with the limited capacity for PM2.5 and PM10 removal, thermal oxidation by incineration is not well suited to treat vapor dominated discharge of process waste streams comprising odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds having commingled gas, liquid, and/or solid phases from the numerous rendering processes. Ongoing research indicates that for the whole world, millions of people die prematurely every year due to anthropogenic particulate and ozone air pollution generated by industrial and energy plants. Therefore, a strong need exists to improve upon the treatment of these various vapor dominated discharge of process waste streams comprising odorous, noxious, hazardous, toxic, mutagenic, and/or carcinogenic compounds and/or precursor compounds having commingled gas, liquid, and/or solid phases.